buffet: Add a helper to coordinate async callbacks

We frequently end up in situations where we want to call an "init
succeeded" callback after many other callbacks indicating partial
init success come back.  AsyncEventCoordinator will manage this
process for us in a general way.

BUG=chromium:360831
TEST=Unittests

CQ-DEPEND=CL:193650

Change-Id: I968a65e88d60199d0355743a2fcee7e20156bc31
Reviewed-on: https://chromium-review.googlesource.com/194362
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
4 files changed
tree: e23c2f061e432674154e656b09b33b0bc5c47857
  1. attestation/
  2. buffet/
  3. common-mk/
  4. .gitignore
  5. LICENSE